The opposite of "cold turkey"

Factual Questions
21

Right, the “oppositeness” that the OP seems to be seeking is for the “cessation” part of this concept. He wants a phrase meaning “abrupt & complete commencement” of some habit.

List of possibilities so far, including previously (non-facetiously) suggested terms, some of which seem to be more focused on comprehensiveness of the endeavor rather than its abruptness:

Baptism of fire
Both barrels
Charging right in
Crash course
Deep diving
Diving headlong
Diving right in
Full speed ahead
Going whole hog
Jumping in the deep end
Jumping in with both feet
Jump-starting
No warmup
Plunging into
Sink or swim
Taking the plunge

22

Damn, that’s what I came in here to say.

23

I’ll suggest YOLO

24

People do say “addicted straight away”… “First try and I was hooked”. “it became a habit”. This is the cliche, so it seems that there is no cliche in lesser words… its normal to get into a habit, its also impossible to say when it became a habit, whereas going cold turkey very likely has a time that occurred … if you say “I became an drug user hot turkey”, it wouldn’t be understood… unless it was a comedy for the high IQ people.

25

Going cold turkey is to stop, hard.

Going ham is to start, hard.